Embodiments of the subject matter herein relate to rail vehicles. Other embodiments relate to rail vehicle trucks.
A diesel-electric locomotive typically includes a diesel internal combustion engine coupled to drive a rotor of at least one traction alternator to produce alternating current (AC) electrical power. The traction alternator may be electrically coupled to power one or more electric traction motors mechanically coupled to apply torque to one or more axles of the locomotive. The traction motors may include AC motors operable with AC power, or direct current motors operable with direct current (DC) power. For DC motor operation, a rectifier may be provided to convert the AC power produced by the traction alternator to DC power for powering the DC motors.
AC-motor-equipped locomotives typically exhibit better performance and have higher reliability and lower maintenance than DC motor equipped locomotives. In addition, more responsive individual motor control may be provided in AC-motor-equipped locomotives, for example, via use of inverter-based motor control. However, DC-motor-equipped locomotives are relatively less expensive than comparable AC-motor-equipped locomotives. Thus, for certain hauling applications, such as when hauling relatively light freight and/or relatively short trains, it may be more cost efficient to use a DC-motor-equipped locomotive instead of an AC-motor-equipped locomotive.
For relatively heavy hauling applications, diesel-electric locomotives are typically configured to have two trucks including three axles per truck, where the three axles include one or more powered axles and one or more non-powered axles. Each powered axle of the truck is typically coupled, via a gear set, to a respective motor mounted in the truck near the axle. Each axle is mounted to the truck via a suspension assembly that typically includes one or more springs for transferring a respective portion of a locomotive weight (including a locomotive body weight and a locomotive truck weight) to the axle while allowing some degree of movement of the axle relative to the truck.
A locomotive body weight is typically configured to be about equally distributed between the two trucks. The locomotive weight is usually further configured to be symmetrically distributed among the axles of the trucks. For example, a conventional locomotive weighing 420,000 pounds is typically configured to equally distribute weight to the six axles of the locomotive, so that each axle supports a force of 420,000/6 pounds per axle, or 70,000 pounds per axle.
Locomotives are typically manufactured to distribute weight symmetrically to the trucks and then to the axles of the trucks so that relatively equal portions of the weight of the locomotive are distributed to the axles. Typically, the weight of the locomotive and the adhesion capability of the locomotive determine a tractive effort capability rating of the locomotive. Accordingly, the weight applied to each of the powered axles times the amount of friction or adhesion that can be developed to the powered axle determines a tractive effort capability of the corresponding powered axle. Consequently, the heavier a locomotive, the more tractive effort that it can generate. Additional weight, or ballast, may be added to a locomotive to bring it up to a desired overall weight for achieving a desired tractive effort capability. For example, due to manufacturing tolerances that may result in varying overall weights among locomotives built to a same specification, locomotives are commonly configured to be slightly lighter than required to meet a desired tractive effort capability, and then ballast is added to reach a desired overall weight capable of meeting the desired tractive effort rating. In conventional locomotive systems, the weight distribution among the powered axles and non-powered axles is statically adjusted prior to shipment, and is not capable of being dynamically adjusted once the locomotive trip has begun.
Accordingly, a locomotive system is needed that may be used to dynamically affect a force applied through a locomotive powered axle or a locomotive non-powered axle of a locomotive truck, so to dynamically adjust a weight distribution among the powered axle(s) and non-powered axle(s).